Picture of the Day: A Lone Black Hole Without a Galaxy

By Rebecca J. Rosen

More than 200 million light years away, at the edge of a galaxy named ESO 243-49, Hubble has spotted a lone, supermassive black hole. The presence of such a black hole, with no surrounding galaxy, is "odd," Wired reports, "because black holes of this size generally form in the centers of galaxies, not at their edges. This suggests the black hole is the lone survivor of a now-disintegrated dwarf galaxy." The black hole, HLX-1, has 20,000 times the mass of our sun. Scientists think that the stars of the dwarf galaxy that once surrounded it were siphoned off into the larger ESO 243-49 when the two galaxies came into proximity with one another. The findings are reported in Astrophysical Journal Letters.